In the pharmaceutical industry, dissolution testing and analysis is required to be performed on samples taken from batches of tablets or capsules manufactured by pharmaceutical companies in order to assess efficacy and other properties. Dissolution analysis by automated means has become popular for increasing throughput and improving accuracy, precision, reliability, and reproducibility. Automation also relieves the tedium of manually performing a variety of requisite procedures, including: handling and delivering dosage units such as capsules and tablets; monitoring dissolution system parameters; manipulating the shafts carrying the agitation paddles or sample baskets; recording, displaying and printing accumulated data and test results; and cleaning and filtering the vessels employed in such procedures.
Despite the benefits accruing from automation, validation of the procedures employed in dissolution testing and analysis remains a critical consideration. A typical dissolution test requires, among other things, that a rotatable shaft equipped with a paddle or basket be properly positioned in the center of and properly located a specified distance from the bottom of, a dissolution test vessel prior to conducting the test. The USP has promulgated guidelines for the pharmaceutical industry which are enforced by the FDA. Under USP 24, General Chapters, Dissolution (711), the shaft must be positioned such that its centerline is not more than 2 mm at any point from the vertical axis of the vessel, and such that the paddle or basket (typically mounted to the lower end of the shaft) be positioned at 25 mm±2 mm from the bottom of the vessel. Similar guidelines specify standards relating to the diameter of the shaft, the angular offset of the shaft and the vessel from a vertical axis, the wobble of the shaft and shaft basket during operation, and the rotations-per-minute (RPMs) of the shaft during operation.
Systems and methods have been developed to automatically acquire the physical measurements relating to the vessel and the shaft, which improved upon various hand-held devices such as rulers, machinist calipers and micrometers, and pass/fail fixtures. These systems and methods reduced the amount of manual handling and reduced reliance on sight and feel when acquiring physical measurements. However, such systems may require attachment of the measurement device to the shaft. The attachment of the measurement device to the shaft may apply force to the shaft potentially disturbing the position of the shaft within the vessel. Moreover, these known systems may require an operator to take multiple readings and reposition the measurement device within the vessel for subsequent readings. This manipulation of the measurement device may further disturb the position of the shaft within the vessel. There accordingly exists a need for an improved apparatus and improved methods for acquiring physical parameters relating to a vessel and a shaft within a vessel of a dissolution apparatus.